This section is intended to introduce the reader to various aspects of art, which may be related to various aspects of the present invention that are described and/or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present invention. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art.
Content, such as multimedia content—e.g. films and music—documents, photos and so on often need to be processed before it is released for the enjoyment of the end user.
Films, for example, pass many processing steps from the actual recording to the release: de-rushing, mixing, addition of digital effects, dubbing, subtitling, and so on.
It will be readily appreciated that a content provider has two requirements for a processing (also called post-processing) system: 1) strict and traceable processing operations, and 2) easy transmission and duplication of the content. The person skilled in the art will appreciate that prior art systems satisfy one or the other requirement, but not both.
Analogue systems generally satisfy the first requirement. As content is stored on tapes or film reels, it is relatively easy to control the processing: a particular content remains with a certain department until the tape is sent to the next department. In addition, it is also possible to trace the tape in case of theft. On the other hand, transmission of the content is less straight-forward, as this requires sending the physical tape, which naturally is difficult, particularly if long distances are involved. It is also difficult to provide the content to more than one entity at once, as the content has to be physically duplicated. In addition, erasing and/or destroying content after use may also provide constraints on the users.
Digital systems provide easy transmission and duplication of content. However, it is much more difficult to control the processing of the content: if the content resides on a server, it is very difficult to control who has access to it and errors may often be made if one department erroneously believes that the previous department has finished processing the content.
FIG. 1 shows an exemplary processing system in which the invention may be used. The system 100 comprises a subtitling device 110, a colour management device 120, a dubbing device 140, a digital special effects device 150, a storage device 160, and an emission clearance device 130, all connected by a network 170.
In the system of FIG. 1, it may for example be required that content pass colour management 120 and digital effects 150 (in no particular order) before being sent to dubbing 140 and optionally further to subtitling 110, before passing through emission clearance 130. As every device has access to the storage 160, it is difficult to control that the workflow is respected.
This difficulty in digital systems is inherent in Digital Rights Management (DRM) Systems. DRM controls access to the content according to usage restrictions. The content is encrypted and a separate license is provided to the end user.
A DRM architecture comprises a content provider, a content distributor, a license issuer, and content users, and has the following characteristics: 1) they are built around the servers, 2) an end user is not allowed to create new content and licenses from the obtained content, and 3) the right to decrypt the content is global—the user either has it or he doesn't.
It will thus be appreciated that most prior art DRM solutions are not appropriate to fulfil the two requirements listed hereinbefore.
International application PCT/EP08/053181 presents a solution in which a workflow for digital content is ensured by having each processing device store a number of rules linking decryption keys and encryption keys. Imagine that digital content is supposed to be treated by a colour management device, a dubbing device and a subtitling device, in that order. The content is ingested into the system by encrypting it using an encryption key for which only the colour management device has the corresponding decryption key. The colour management device stores a rule stating that content decrypted using the decryption key should be encrypted using an encryption key for which only the dubbing device possesses the corresponding decryption key. The same scheme is applied to the other devices. As such, the workflow is ensured.
While this solution works well in many cases, it can in some instances be difficult to manage the keys in the system, especially when the content is to be treated by external devices.
It can thus be appreciated that there is a need for an alternative solution that enables a processing system in which digital content may be easily distributed and duplicated, while it also imposes strict processing operations, this solution being called Digital Processing Management (DPM).
The present invention provides such a solution, with a number of variants.